Effect of methabenzthiazuron on growth and nitrogenase activity in Vicia faba

The effects of the herbicide methabenzthiazuron (175 and 220 g ha^-1) on vegetative and reproductive growth, nodulation and nitrogenase activity of Vicia faba were studied in the field under Mediterranean conditions. Nitrogenase activity of excised nodules was estimated using the acetylene reduction assay four times during the developmental period. Leaf area index, dry weight and nitrogen content of the different parts of the plants were measured. Methabenzthiazuron-treated plants showed an increase in nodulation, nitrogenase activity and vegetative growth at early pod fill. Methabenzthiazuron also caused an increase in leaf N content and fruits. These were transient effects found during early and mid pot fill. Nevertheless, plants treated with these sublethal doses of herbicide improved seed production and nitrogen content of seeds at harvest time. The stimulatory effect of methabenzthiazuron on N₂ fixation and vegetative growth seems not be related with the transient stimulatory effect on photosynthetic capacity, also caused by the herbicide, since the stimulatory effect on N₂ fixation was apparent during pod fill, when photosynthetic capacity declined and was not modified by methabenzthiazuron.     

Cloning and expression of hepatitis B surface antigen in the yeastKluyveromyces lactis

Summary The gene coding for the major surface antigen of the hepatitis B virus was integrated into the genome ofKluyveromyces lactis and expressed up to levels of 0.4% of the total soluble protein.     

Detection of linkage for heterogeneous disorders by using multipoint linkage analysis.

We have compared the efficiency of the lod score test which assumes heterogeneity (lod2) to the standard lod score test which assumes homogeneity (lod1) when three-point linkage analysis is used in successive map intervals. If it is assumed that a gene located midway between two linked marker loci is responsible for a proportion of disease cases, then the lod1 test loses power relative to the lod2 test, as the proportion of linked families decreases, as the flanking markers are more closely linked, and as more map intervals are tested. Moreover, when multipoint analysis is used, linkage for a disease gene is more likely to be incorrectly excluded from a complete and dense linkage map if true genetic heterogeneity is ignored. We thus conclude that, in general, the lod2 linkage test is more efficient for detecting a true linkage when a complete genetic marker map is screened for a heterogeneous disorder.     

Identification of vitellogenin in the ant, Camponotus festinatus: changes in hemolymph proteins and fat body development in workers.

Vitellogenin has been identified in the ant Camponotus festinatus, both in queens and workers. In the workers, it is already present before adult eclosion in low concentrations (less than 1 microgram/microliter hemolymph). Vitellogenin and vitellin are immunologically identical and are composed of a single type of apoprotein with an apparent Mr = 185,000. The molecular weight of the native molecules was estimated as approximately 460,000 by pore limiting gradient electrophoresis. Vitellogenin was detected as a major protein in the hemolymph of young workers, both under queenright and queenless conditions. Thus, in spite of their sterility in the presence of the queen, C. festinatus workers are able to synthetize vitellogenin which is identical both in size and immunologically to the queen vitellogenin. About 6-7 weeks after adult eclosion, however, vitellogenin was usually undetectable in the hemolymph of queenright workers, particularly the minor workers, while it constituted about 30% of total protein in queenless workers. Protein concentration in the hemolymph of queenless insects increased up to 20-fold as compared to 1-day-old insects. Queenless workers also developed large amounts of perivisceral fat body, while queenright workers, particularly the minor workers, showed a dramatic fat body regression about 6 weeks after emergence.     

Can water mites control populations of planktonic Cladocera?

Predatory pelagic water mites, Piona sp., in a small subtropical lake of Argentina showed rapid numerical response and protection from fish consumption. In experiments, predation rates of Piona on cladocerans equalled those of the principle lake planktivore, Moenkhausia intermedia Eigenmann (about 100 prey · predator^–1 day^–1). As a result, the mites caused a summer depression in the dominant lake zooplankter, Daphnia laevis Birge, evidenced by the analysis of its population dynamics and simple modelling.     

Amino acid sequence of neurotoxin III of the scorpion Androctonus austrialis Hector.

The amino acid sequence of neurotoxin III, purified from the venom of the North African scorpion Androctonus australis Hector, has been determined by Edman degradation using a liquid-phase sequencer. Carboxypeptidase A hydrolyses confirmed not only the sequence of the five last residues but also the presence of a free alpha-carboxylic group at the C-terminus. Edman degradation was conducted on one hand with the Quadrol [N,N,N',N'-tetrakis(2-hydroxypropyl)ethylene diamine] program and S-alkylated protein before or after coupling with sulfophenylisothiocynate (the first 34 residues were thus identified), on the other hand on tryptic and chymotryptic peptides with a dimethylbenzylamine program (residues 1--23 and 31--34 were confirmed, the positions of residues 35-64 were established). Neurotoxin III was found to belong to the same group of scorpion toxins active on mammals as neurotoxin I purified from the same venom (50 homologous positions exist in the two proteins).